Automatic stop for traversing hoists



Dec. 16, 1941. G H Nl uEf f 2,266,196

AUTOMATIC STOP FOR TRAVERSING HOISTS Original Filed Dec.-- 29, 1938 SPARK con N\ 366mm Gear- 9e Ian/62M.

Patented Dec. 16, 1941 UITE AT S PAT T Fries AUTOMATIC STOP FOR TRAVERSING HOISTS George Haniquet, Glendale, Calif.

Original application December 29, 1938, Serial No.

248,353. Divided and this application September 13, 1939, Serial No. 294,757

2 Claims.

This invention relates to improvements in derricks, particularly of the type which can be readily transported from place to place. The particular adaptation in mind of the invention is to telephone work. However, the invention is not limited to this particular use because it is capable of application to derricks for other purposes, in fact any use requiring an automatic stopping of the hoisting machinery in the event that an abnormally heavy load is imposed upon the derrick boom.

The details of the latter are not disclosed hereing because the instant application is a division of an application for patent for Automatic portable derrick filed by George I-Iam'quet, December 29, 1938, Serial No. 248,353, and said details being fully brought out therein. Said derrick includes hoisting machinery which, obviously, fundamentally is an engine. It is desired to avoid putting too heavy strains either upon the engine or the derrick boom, and to that end the object of the invention is as follows:

To provide a derrick in which a load-limiting device is embodied in the boom, saiddevice being coupled with an appropriate means for automatically opening an ignition circuit switch if the boom is put under a load so great that the raising of it will endanger the mechanical structure.

Other objects and advantages will appear in the accompanying specification, reference being had to the accompanying drawing in which,

The single figure is a partially sectional and elevational view of the free end of the boom, particularly illustrating the load-limiting device as well as a diagrammatic representation of the engine and its ignition circuit.

In carrying out the invention provision is made of a boom generally designated I. This boom comprises an outer tube 2 of a suitable metal, either round or non-circular in cross section. This tube is open at its ends, the upper end 3 being of particular concern herein.

At the free end 3 of the boom tube 2 there is a load-limiting device commonly designated l8. This device consists of a tubular insert l9 which has an integral partition 20 contiguous to its inner end and carries a sheave fork 2| at its'outer end. The sheave fork consists of duplicate plates 22 which are made integral with a plate 23. This plate is welded to the tubular insert l9 so as virtually to be an integral part of said insert. Matching slots 24 in the insert I!) make room for a cross bolt 25 which limits the extension of the insert 19 under the influence of a heavy spring 26 which presses against the partition 20.

For the purpose of the spring the boom tube 2 also has a partition 21 against which the spring 26 is rested. An electrical switch 28 is attached to the partition 21. This switch may comprise an ordinary closed type automobile stop light switch. It has a movable plunger 29. One end of this plunger projects through a hole 30 in the partition 21 because of the tension of a spring (not shown) which tends to keep the plunger in the projected position. A stud 3| on the partition 20 is adapted to be held spaced from the plunger 29 by the spring 26. -When an overload is imposed on the sheave in the fork 2|, the recession of the tubular insert l9 into the boom tube 2 against the tension of the spring 26 brings the stud 3! into engagement with the plunger 29, a sufficiently continued movement actuating the switch 28 to open an electrical circuit, herein regarded as comprising the ignition circuit of the truck engine E. This circuit is commonly designated 32.

The wires of this circuit embrace an ignition switch 33 and a relay 34 which acts in the capacity of an auxiliary ignition switch. When the ignition switch 33 is manually closed the resulting magnetization of the relay core attracts the relay armature 35 and completes the ignition circuit which can be traced through the spark coil and timer. The relay may be conveniently mounted anywhere on the carrier of the boom, for example on the dash-board of a truck not shown. The engine E is adapted to operate a hoisting means, which may consist of the drum 36 on the engine shaft. One end of a hoist cable 36 is wound on this drum, said cable being trained over the sheaves 38 mounted in the fork 2!.

As long as the derrick is being operated under safe conditions the switch 28 remains closed, but

when the derrick is subjected to an overload in the manner indicated, the depression of the plunger 29 and consequent opening of the switch 28 will automatically open the ignition circuit 32 and stop the engine E. Said opening of the switch 28 and circuit 32 deenergizes the relay 34 to accomplish the purpose stated.

The operation is already understood. The cable 36 is applied to the sheave 38, the free end of the cable being attached to the load. The engine E may be either the engine for propelling the machinery of the truck, or it may comprise an independently carried power device. In either event it is adapted to operate a hoisting means, shown to comprise the drum 36 The engine is controlled by the ignition circuit 32 which, as

rin

previously explained, is maintained in the closed position by the normal closure of the switch 28. The spring 26 resists the recession of the insert l9 inwardly of the boom 1, but when the load imposed on the sheave 38 exceeds the tension of the spring 26, the collapse of the latter results in an opening of the switch 28, an opening of the ignition circuit 32, and the stopping of the engine E. The automatic control thus afiorded is regarded as being of considerable importance in that it insures the avoidance of damage to the derrick mechanism.

I claim:

1. In a derrick having a boom, said boom having a tubular open end, a sheave situated adjacent to the open end of the boom for the support of a cable, a tubular insert carrying the sheave and being telescopically slidable in said open end, means loosely tieing the insert and boom end together, said looseness providing for a limited telescopic movement of the insert with respect to the boom end, confronting partition means respectively situated internally of and afiixed to the boom and the insert, a spring emplaced between and in contact with said partition means, thereby being centered on the axis of the boom and tending to extend the insert to the limit of its telescopic movement in one direction, and an electrical switch situated internally of the tubular boom end and having coacting portions respectively carried by said partitions for operation of the switch by the movement of one partition relative to the other upon a counter-movement of the insert due to a load on the sheave.

2. In a derrick having a boom, said boom having a hollow free end, stop means on the boom in crosswise relationship to said end, a sheave situated adjacent to said free end for the support of a cable, sheave-carrying means in telescopic relationship to said end and having a slot occupied by said stop means, an electrical switch, a member carried internally of the hollow boom end having the switch attached thereto and thereby to enclose the switch, a spring having one end rested on said member, a stud to actuate the switch by a movement of the sheave-carrying means under a load to compress the spring, and a member carried by said sheave-carrying means, providing a mount both for the stud and a rest for the other end of the spring.

GEORGE HANIQUET. 

